1. Technical Field
The present invention relates to a polymerizable composition, an ink composition for inkjet recording, an inkjet recording method, and a recorded matter.
2. Related Art
A polymerizable composition, which contains a polymerization initiator and a polymerizable compound and which is cured when active species that have been generated from the polymerization initiator by application of energy allow the polymerization of the polymerizable compound to proceed, is used for various applications; for example, a curable type ink composition, a coating agent, a painting material, and an image recording layer of a lithography plate.
There has been a demand for the polymerizable composition to cure with high sensitivity under application of energy and to form a cured film. However, a problem exists whereby, when high sensitivity is realized, an undesired curing reaction occurs due to heat or light, which results in reduced storage stability.
In terms of the use of the polymerizable composition, in particular, an ink composition for inkjet recording, which forms an image on a recording medium such as paper based on an image data signal, enables recording using an inexpensive apparatus. In addition, since an image is formed directly on a recording medium by discharging ink only onto a required image area, the ink can be used efficiently, and the running costs are low. Moreover, in the inkjet recording method, there is little noise. Accordingly, the inkjet recording method is excellent as an image recording method.
According to the inkjet recording method, it is possible to print not only on plain paper but also on a non-water absorbing recording medium such as a plastic sheet or a metal plate. Here, realizing a high printing speed and a high image quality in printing is an important issue, and the time needed for drying and curing the droplets after printing exerts significant influence on the productivity of printed matter and the sharpness of the printed image.
As one inkjet recording methods, there is a recording method using an ink for inkjet recording, the ink being curable by application of energy such as irradiation of radiation. According to this method, by performing irradiation of radiation, immediately after jetting an ink or when a specific period of time has elapsed since jetting the ink, thereby curing the ink droplets, the productivity of printing can be enhanced and a sharp image can be formed.
In an ultraviolet ray curable ink composition, excellent curability is required, and furthermore, for example, when an ink image is formed on a thermoplastic recording medium, the adhesion between the base material and the formed image, namely, the cured film, is required. Therefore, for the purpose of appropriately adjusting the crosslink density or the molecular weight, a chain-transfer agent, such as a thiol compound, is added to an ink composition. However, when the addition amount of the chain-transfer agent is increased, the storage stability of the ink composition tends to be lowered. In present circumstances, it is difficult to realize both the preservation of appropriate physical properties and storage stability.
As an example of a curable composition that is capable of being cured by irradiation with actinic energy rays, a curable resin composition, which includes an acrylic acid ester, a phenol-based antioxidant, and an organic phosphinic acid, and exhibits excellent curability, and in which discoloration of the cured film is suppressed, has been proposed (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2013-23630).
It is disclosed that in this curable composition, a monofunctional α,β-unsaturated compound, for example, methylenemalonic acid, may be used as a polymerizable compound having a low molecular weight.